This article is intended to present two accomplished metalshaper’s methods for tuck shrinking. They made four albums covering tuck shrinking tools, tuck shrinking and annealing aluminum. Each album was created to be combined with the others to make a complete article. The albums have expanded text explanations with each photo to help explain what John and Pat are trying to demonstrate. The idea was to use MSA’s upgraded photo albums to have a series of photos simulate as close as possible what you would see and hear if you visited John and Pat in their shops. In each album they have tried to point out the little things that they look for when tuck shrinking. Knowing that learning is a process, they have also shown common mistakes and how to overcome them.
Metalshaping or creating shapes in a panel involves manipulating a flat sheet of the metal by stretching or shrinking the metal to form a compound curve. Shapes that require compound curves to make are a simple bowl, Model A fenders, aircraft skins, motorcycle tanks and many vintage race car bodies.
Miller Golden Sub, John Glover made a new body skin in 1971.
Pat’s first motorcycle gas tank made last fall.
Stretching is usually accomplished by using a mallet and bag, hammer and dolly, e-wheel or a variety of other tools. As the metal is shaped by stretching, the metal thins making the overall surface area increase. This picture is an example of a shape that has been formed by stretching on a power hammer. It is a blister that has been formed in a flat piece of metal. The blister is 8” across and about 3” deep.
Shrinking is a process that is accomplished by creating ruffles on the edge of a panel and crushing them down in such a way that cause the edge of the panel to shrink. Another way of saying this is that you gather the metal together as you smooth the sides or compress the tucks. You can measure how much you have shrunk a panel by making two lines on the outside of your tuck. Then measure the distance along the edge the panel before you start to make a tuck and measure the distance between the lines after you have completed your tuck. The difference between the starting and the ending measurement is the amount you have shrunk the panel.
If you have not seen tuck shrinking completed, visualize a round piece of metal. Now take the circle and press it down over a baseball or softball. The result would have ruffles, tucks or extra material on the sides of the ball. To make the sides of the metal smooth, the excess metal will need to be brought together or gathered. If you gather the ruffles or tucks together, the metal would be thicker on the sides than at the bottom of the shape.
|This picture is to show what the tucks might look like if they were all formed at once around a disk. The shrinking would take place when the tucks were hammered down to form a smooth edge.|
The motorcycle tank at the top of this article was made from scratch by Pat Groover utilizing stretching, shrinking and hammer welding several pieces of metal together. When, what, where, and how you use stretching or shrinking to form a shape are the questions that you will need to ask before you begin each project. Depending upon your knowledge and skills, and also tools that are available, you determine the best method to be used.
Imagine that you need to create a shape with a dish over 3” deep in a panel that is over 18’ inches across. If you attempt to make a panel that is this large only by stretching, it will require a lot of stretching and working of the metal all over your shape. At the dome of the shape, you will have substantially thinner material than at the edges.
If you have the ability and tools to shrink the edges of your panel, edge shrinking will greatly reduce the effort to make your part. The resulting piece will also be stronger because the metal in the entire shape will be thicker. There are numerous ways to shrink. You can use tools such as hand operated shrinkers, larger tools include power hammers and Pullmax type of machines equipped with a shrinking tool or thumbnail die. You can also cut out V’s and weld them closed. Another method would be to shape two or more small panels and weld them together, or for smaller pieces you can use forming heads and slappers.
If you are familiar with the hand tucking method, the tucks are made cleanly and relatively fast to shrink the edge of the panel. The tucking process for large panels is such that all three sizes of tucks shown in this article, large mallet formed, combined with the intermediate and small twister formed tucks would be used. As you get nearer the edge, smaller tucks will be required to provide final tightening of the shape to meet your requirements.
Our focus in this particular article is specifically how to use the hand tucking method of shrinking. We are using the term “hand tucking” to clearly differentiate this skill from other methods of shrinking using hand tools or machines. Hand tucking or tuck shrinking is a skill that is quickly learned by a person familiar with sheet metal work. One of the reasons that tuck shrinking is so valuable a skill is that it allows you to precisely locate where the shrinking occurs. As you develop the skill of tuck shrinking, you can increase or decrease the size of tuck to control how much you shrink the edge of your panel. Tuck shrinking has the following benefits:
- Low Cost, only two or three hand tools are required
- Ability to control the location and amount of shrinkage
- Shrinking speeds up the process of making the panel by allowing you to effectively combine shrinking and stretching to achieve the shape you desire to create.
- It is especially beneficial when used on larger panels, usually over 14” across
To tuck shrink by hand as shown in this article, you will need three tools:
- A small easy to make tool called the “Tucking tool” (sometimes called a twister). This tool is usually fabricated in two sizes to form the small to medium sized tucks.
- For the larger tucks that large panels require, a mallet is necessary.
- A domed post head or forming head of a particular design, known as the universal head.
These tools and the methods to use them are detailed step by step in pictures and text contained in the albums listed below. The total article includes this introduction, four albums that contain over 130 pictures and a Question and Answer section.
This is an introduction to the techniques for tuck shrinking that John learned as an apprentice and has continued to develop since 1943. The first series of photos shows the tools John uses. The next series of photos show John manually creating a large tuck, over 5” deep with just a hammer and forming head. He documents each of the steps that he uses to make, set and hammer down the tuck. Then John created a series of pictures demonstrating how a tuck is made with a “twister” or “tucking tool” and mallet. Throughout the pictures, extra information like how much shrinkage can be accomplished with different size tucks are provided to give a beginner a goal of what is possible. Finally, he shows several common mistakes people make when learning tuck shrinking and how they can be corrected. All of John’s work in these photos was completed on steel panels.
In Pat’s photo albums he documents how he tuck shrinks using tucking tools. After the first series, he shows the effect on panels when you have completed shrinking multiple tucks. He shows an alternative way that some beginners find helpful when they are learning. Several common mistakes and how to correct are also included. He also shows the size and shape of tucks made using several different tools Finally he shows what a panel looks like after a series of passes are done on big machine with thumb nail shrinking dies. All of Pat’s work is done on aluminum panels to provide more than one material.
This album was created by John to show his hammer, forming head and the process he uses to make a tuck tool. Measurements are provided so someone at home could make themselves a hammer and tuck tool. Commercial sources of hammers and forming heads are also provided in the question an answer section.
Many people prefer to anneal or soften aluminum to make it easier to shape. The softer annealed aluminum is especially helpful for beginners learning to tuck shrink or practice metalshaping. This album is an overview of the process on 3003 and shows many common mistakes made by the beginner. Note: The FAA has specific rules regarding annealing and hardening of metals, reference FAA AC 43-13B Accepted Practice. Unless specifically authorized by the manufacturer, a structural member or panel of any vehicle should not be annealed for safety reasons.
We suggest you start with John’s Tuck Shrinking album, proceed through Pat’s tuck shrinking album and then view the tools or annealing album if you would like further information. Each of these albums has full text descriptions in the detail, so it is important to click on the first picture in an album to enlarge it. The expanded windows show the detailed text (not the thumbnails) and you just press the Next button to see the next picture or use the Previous button if you want to go back and see a picture again. We have tried to provide many small details that will make it easier to understand and master tuck shrinking. Links to the other albums are provided in the final picture of each album to allow you to go to the next part of the article.
Tuck Shrinking Basics
We hope that you find this information helpful.
Tuck Shrinking or Twister Specifications
|Shape||Size/Type||Length||Tip Length||Distance Between Tips||Bend||Total Material To Buy|
|Small Twister||T Handle 3” Across||5/16” Round Rod||3”||1”||3/16”||2.5” from tip||9”|
|Medium Twister||L Handle 6-8” long||1/2” Round Rod||10”||3”||¼”||4” from tip||28”|
|Medium Twister – No welding alternative||L Handle 6-8” long||3/4 x 5/16 or 1 x ½ Bar Stock||10”||3”||¼”||4” from tip||18”|
John Glover’s Tuck Shrinking Plastic Hammer Specs
|Face Size||Head Length||Edge Radius||Approx Weight||Handle Length|
|Medium||2 x 3||4 3/4||3/8”||2 to 2 ½ pounds||15”|
Notice: Working in a shop, fabricating metal parts and metalshaping require the use of tools and techniques that require a full understanding by the operator. Please wear eye and ear protection at all times. The information contained in this article is true and complete to the best of our knowledge. All recommendations on tools, parts and procedures are made without guarantees on the part of the authors or the Metalshapers Association. Authors and Metalshapers Association disclaim all liability in connection with the use of this information.
This article is a collaboration of three people each with different perspectives and skills in metalshaping:
If you are a beginner or expert member, we want to make clear that there are many ways of accomplishing metalshaping and in some cases people may use definitions that may be slightly different. This article is intended to demonstrate one very effective way to shrink, specifically “tuck shrinking” by hand. You may have or will develop different techniques to accomplish shrinking or tuck shrinking. In fact, the authors encourage you to experiment to find the best methods for you and the type of projects or work that you make.
John Glover, a master craftsmen and true panel beater in the old world tradition. He started as a metalshaping apprentice in England when he was 14. During his 50 year career he worked at Ford, Chevrolet, DeHaviland and GM building the panels for aircraft and prototype cars. Along the way, he has also build the bodies of numerous specials and recreations of historic vehicles. He has conducted many seminars for beginners and at GM since his retirement in 1991. Supposedly retired, he is constantly convinced to share his knowledge and passion for metalshaping by writing books and making videos that demonstrate metalshaping skills. He has also designed a series of wheeling machines and tools sold by MetalCraft Tools, www.metalcrafttools.com. He is leisurely working on a new book that explains metal working methods that are used in large experimental shops, but are not documented or generally known about. Pat Groover is also an accomplished metalshaper. He spent his career in the Air Force and aviation industry, retiring in 2000. He began studying metalshaping in 1995. Since his retirement, he has become a leader in reaching out to people to help them start and learn the skill of metalshaping. He has run a metalshaping demonstration tent at the Sun n Fun Fly In for the last 4 years. This is a favorite spot for attendees of Sun n Fun, where people stop by and are shown how to use a complete selection of metalshaping equipment, from Power Hammers, Pullmaxes and e-wheels to simple hand work making bowls with a mallet, sand bag and forming anvil.
Patrick Thompson is an automotive and metalshaping enthusiast who contributed coordination and editing. When Pat and John started sending pictures of their work, he considered taking up boating. He added a novice perspective and asked questions to draw out additional details from John and Pat.